The introduction of securities margin trading has changed the unilateral market making of chinese stock market and improved the trading mechanism of China's securities market.The innovation of this paper is that it uses data before and after the introduction of securities margin trading to analyze the impacts of margin trading to the effectiveness of Chinese stock market using many econometric models, including ADF unit root test, co-integration test, Granger causality test, OLS regression, impulse response analysis and variance decomposition through Eviews6.0 statistical software. Moreover, the data used includes nearly five years of margin trading, which increase the reliability of conclusions.